Apparatus for canning foods



May 30, 1933. G. s. BOHART 1,911,879

APPARATUS FOR CANNING FOODS Filed Aug. 27, 1950 Ill/l Patented May 30, 1933 UNITED STATES GEORGE S. BOHABT, OF BERKELEY, CALIFORNIA APPARATUS FOR CANNING FOODS Application filed August 27, 1980. Serial No. 478,263.

This invention relates to improvements in processes and apparatus for canning foods. In the usual method of canning foods, the food product to be treated is first preheated and then deposited in the open container. After sealing, the can is cooked either in boiling water or in a steam retort under pressure for a period of time sufficient to insure the destruction of the most resistant spoilage organisms.

The determination of a safe process for canning food depends upon the temperature at the center of the can and the time required at different temperatures to destroy spoilage bacteria. As noted, in the usual process, of which canned corn is an example, the mass is cooked in the steam retort at 250 F. for approximately seventy-five minutes. This extended period is required to o insure the penetration of heat to the center of the mass. If this heat penetration factor could be eliminated, a cook of only ten minutes would sufiice for the purpose of sterilization. Heretofore during processing, the portion of the food contents near the wall of the can has been cooked at the maxi mum temperature for practically the entire period, while the material at the center of the can reaches the maximum temperature,

if at all, only at the very end of the period.

As a result, much of the food product may be'overcooked and, in the case of some materials such as corn, may lose its natural color and fiavor.

It is an object of the present invention to provide a process of sterilizing foodin which the maximum sterilization temperature at the center of the container may be reached sooner than by prior methods.

Another object is to provide a method of electrical sterilization of foods.

- Yet another object is to provide a novel type of food container sterilization of foods.

A further object is to provide a novel method of preheating foods which are subsequefitly canned.

. With these and other equally important objects in view, the invention comprehends the treatment of food to be canned in a permitting electrical mately one and three-quarters minutes.

specialtype of container whereby the material is subjected to electrical heating effects and thereby heated quickly and uniformly to the desired sterilization temperature.

In order to enable a ready comprehension of the invention, a typical physical embodiment is shown in the single figure of the aocompanying drawing, showing a food container connected to means. y

The purpose of the present invention is to obviate the protracted thermal. treatment necessary in the prior processes and thereby insure a uniform, properly cooked product.

Broadly considered, the invention involves the concept of sterilizing canned food in hermetically sealed containers electrically.

I have foundthat if a food product, such as corn, is admitted to a container and the product treated to insure bacterial contamination, it may be sterilized in the container in a very short period of time, by subjecting itto the heating effects of an electrical current. As will be a preciated, a relatively wide range of speciiie types of cans maybe employed. I prefer, although I do not in-' tend to be limited specifically to thistype, to employ a can havin a non-conducting body and cond'gicting ends. 8

0 shown in the drawing, such a structure may comprise the body 1, which may be constructed 0 'terial, such as glass,

suitable non-conducting macelluloid, or. the a like, and the conducting metallic ends-2'and 3 reslpectively. I 1

have found in my experimentation that when such a container was filled withuncooked cream style corn, preheated to 182 F. and it was then sealed and an alternating current of 60 cycles, -7 amperes, and 110 volts applied the temperature at the center of the can was raised to 250.F. in approxi- In order to insure sterilization, the temperature was maintained at this point'for about ten minutes-bi; reducing the current. The prod uct was t en allowed to cool and upon examination exhibited a color similar to that of corn cooked on the cob andsuperior to an electric heating corn processed in the can in the usual manner.

The same improved results were found to obtain when. preparing other food products. For example, a lot of spinach was prepared using the same type of container. This material was blanched for five minutes at 180 F. and hot brine was then added. The material in the can was then subjected to the "action of an electric current of 60 cycles, 5 amperes and 110 volts. At the end of approximately five minutes and eighteen seconds, the temperature at the center of the can reached 250 F. To insure absolute sterilization, this'temperature was maintained for six minutes by reducing the current.

From these experiments, it is obvious that this electrical method of processing presents decided advantages over the usual method involving the application of, so to speak, extraneous heat. When food is sterilized by this electrical method, the material in the center of the container is heated just as rapidly as the material near the outside portions ofthe can and may be adequately sterilizedby'a cook of ten minutes or less. By reason of this short cooking period, the product largely retains its natural characteristics of color and flavor. j

The examples given disclose the efli cacy of the method because both corn and spinach are products in which the heat penetration is very slow.

In actually-carrying out the process commercially, the material to be treated may be preheated and admitted to' the containers hereinbefore described. The top 2 may be sealed on and the material after being added to the container may be subjected to the electric heating. This may .be done by placing the bottoms of the cans upon a metallic plate 4, which is connected at one end to a conductor leading to a source of alternating current. The plate 4 may be of considerable length so as to be sufiicient to accommodate a large number of cans at one treatment. The other terminal of the electric heating unit may comprise a metallic bar 6, spaced above the top of the can to which are con- 1 nected a plurality of metallic contacts 7 For the purpose of simplicity, these contacts are shown as a leaf spring which makes good electrical and mechanical connection with the top of the can. The metallic member 6, similarly to the corresponding member 4, is connected through a conductor 8 to the source of alternating current. When the current-is turned on the top and bottom of the can become in effect two electrodes connected to a current source and the material within the can is subjected to uniform resistance heating. Continuous methods may also be employed by providing suitable means for holding the ends of the container in position during the application of the heating current at the same time the cans travel along a conveying device. This may be accomplished by chucks ,which exactly engage and press against the ends of the can with sufficient force to withstand the internal pressure developed during heating of the contents, or by passing the cans through suitable valves on to a conveyor in electrode; when the current is reversed they are impelled in the opposite direction. It is therefore possible, aside from the heating effect, that the frequency of the current may have a decided effect upon the time and temperature necessary for sterilization.

This general method of treatment in addition to sterilizing food products may also be employed for the exhausting of canned foods; Thishas been done experimentally by providing a glass cylinder having a metallic base to which was connected one terminal'of an alternating current source. metallic disc connected-to the other conductor from the alternating current source was suspended above the top of the condenser in such a manner as to contact with the food product therein. The temperature oftoma-' toes was raised from 67 F. to 200'F. in

four and a half minutes by employing an A similar result may only does it decrease the time necessary for processing but it insures a properly cooked material without the dangers and undesirable results of localized overheating. The

container itself maybe made up of readily available materials and may be treated in large numbers; the process, therefore, is

readily susceptible to economic commercial production methods.

The particular embodiment of the invention shown in the drawing, it will be understood, is given merely by way of example. It will be appreciated that a current regulating means may be interposed in the circuit so as to out down the temperature after the desired maximum has been obtained so asto hold this tem erature constant or any predetermined period. Similarly while the use of an alternatin current has several advantages, as herein efore pointed out, the invention is not necessarily limited to this as direct current may be employed to advantage. It is to be understood, therefore, that the invention is not intended to be limited tothe specific apparatus shown or the process described except as such limitations are clearly imposed 'by the appended claims.

I claim;

1. A food container comprising an elec-' trically nonconductive, uninterrupted body portion, having closures at the ends thereof, the space between said closures being unobstructed, and said closures being formed at least in part of an electrically conductive material and directly exposed to the contents of the container whereby the contents may be subjected to a current of electricity. 2. A food container comprising an electrically, non-conductive body portion, having metallic closure members at the ends thereof, the space between said closure-members being unobstructed, and said closure members directly ex osed to the contents of the container where y the contents may be subiected to an electrical current. 3. A food container comprising a body portion formed of glass, having metallic closures at the ends thereof, the space between said closures being unobstructed, and said closures being directly exposed to the contents of the container, whereby the contents ma be subjected to an electrical current. testimony whereof I afiix my signature.

- GEORGE S. BOHART. 

